In the field of electronic integrated circuits, a number of different technologies and processes have been developed, resulting in the availability of a number of different families of integrated circuit types. Two examples which are discussed herein are bipolar and CMOS. Each of these families has its own advantages and disadvantages, in terms of operating speed, density, power consumption, cost, noise immunity, and other factors. The choice of integrated circuit type for a given application is often a balancing of these various factors. Because different IC types are best suited for different applications, there will be situations in which different IC types are brought together in a single system. However, this presents a problem in terms of interconnections, because the different technologies use different voltages, polarity and other electrical parameters. This leads to the need for various types of external level shifting and signal translation circuits, but this adds to the cost, space and power requirements for a system.
The present invention provides a level shifter circuitry on board a chip of one IC technology, to thereby provide the necessary level shifting and interface for direct connection to an IC of another technology. The preferred embodiment is directed to providing signals from a bipolar IC to a CMOS IC. One application for the invention would be in a system which uses a CMOS microprocessor, with bipolar supporting circuitry, where it is necessary for the bipolar IC to send logic signals to the CMOS IC.